An image forming apparatus such as a copying machine and a printer utilizing electrophotographic method is provided with an electrophotographic photosensitive member. In such image forming apparatus, the electrophotographic photosensitive member is rotated by a power transmitter, and synchronously with the rotation, operations such as electrification, exposure, development, transfer, and cleaning are repeated, thereby forming an image on a recording medium.
Specifically, in the image forming apparatus, the electrophotographic photosensitive member is electrically charged at its surface and then rotated while being irradiated by laser light for exposure, according to an image pattern, so that an electrostatic latent image is formed on the surface of the electrophotographic photosensitive member. Next, the latent image is developed by attaching toner to the photosensitive member. The toner attached to the electrophotographic photosensitive member is transferred to a recording medium. After the transfer of toner to the recording medium, the electrophotographic photosensitive member is rotated while a cleaning blade is pressed onto the surface of electrophotographic photosensitive member, so that remaining toner is removed.
An electrophotographic photosensitive member is known which is a combination of a metal body and a photosensitive layer made of Si inorganic material formed on the body.
For forming the photosensitive layer using an inorganic material, a film forming device such as CVD device and sputtering device issued. When forming the photosensitive layer using such devices, generally, the body is heated to an adequately high temperature, e.g. 200° C.-400° C. It is known that the photosensitive layer made in this way may peel off from ends of the body.
It is considered that such peeling of the photosensitive layer is caused due to the difference in rate of thermal expansion of the body and the photosensitive layer. When the body and the photosensitive layer are cooled after the film forming, because of the difference in rate of thermal expansion, the body and the photosensitive layer have different amount of thermal contraction. As a result, a stress is applied between the photosensitive layer and the body, and the stress is trapped within the photosensitive layer. Such internal stress acts largely on the ends of the body where the thermal contraction is the largest, and thus the photosensitive layer peels off from the ends of the body.
The peeled photosensitive layer may stick to a latent image area of the photosensitive layer, which may cause a defective image.
Patent Document 1: JP-B-07-19068
Patent Document 2: JP-B-2514198